A hydraulic excavator as a typical example of the construction machine is generally constituted by including an automotive lower traveling structure, an upper revolving structure rotatably mounted on the lower traveling structure through a revolving device, and a working mechanism mounted on a front part of the upper revolving structure, capable of moving upward/downward. The hydraulic excavator is to perform an excavating work of earth and sand and the like by using the working mechanism while revolving the upper revolving structure.
The working mechanism of the hydraulic excavator is constituted by including a boom provided on the upper revolving structure, capable of moving upward/downward, an arm provided rotatably on a distal end side of the boom, and a bucket provided rotatably on a distal end side of the arm. The boom, the arm, and the bucket are driven by a cylinder device constituted by a hydraulic cylinder and the like, respectively.
The cylinder device is constituted by including a tube having a lengthy cylindrical shape in which one side in a length direction is closed as a bottom part, while the other side is a rod guide, a rod having one side mounted to a piston in the tube and the other side protruding capable of extension/contraction from the rod guide side and having a cylindrical boss part mounted to a protruding end side, and a lengthy plate-shaped protective cover having one side in the direction supported by a cover guide provided to the tube in order to protect the rod, and having the other side mounted to the boss part. This protective cover suppresses collision of the earth and sand, stones and the like against the rod protruding from the tube during the excavating work and protects the rod from these earth and sand (Patent Documents 1 to 3).